Summary:

HIV-1 can develop multidrug resistance in patients receiving various
combination chemotherapies. This is one of main problems in anti-HIV/AIDS
chemotherapy. To identify compounds active against HIV-1 drug-resistant
strains, project partners plan to synthesise and investigate the structure,
conformation and selected physicochemical and biological properties of a
range of new and known, modified 2’, 3’-dideoxynucleoside analogues.

Compounds of this type should act as competitive drug-resistant reverse
transcriptase (RT-Res) inhibitors. Slow releasing forms of these compounds
(prodrugs) will also be prepared. Drug-resistant reverse transcriptases will be
obtained from engineered HIV-1 drug-resistant mutants, as well as by
recombinant techniques. Interactions of synthesized compounds with the wild
type HIV-1 RT, as well as with HIV-1-Res RT, will be investigated and potent
inhibitors will be subjected to antiviral activity determinations in cell cultures
and in vitro cytotoxicity.

Structure-activity relationships will be performed and selected RT inhibitors will
be subjected to determination of complete cross-resistant profiles in laboratory
and clinical HIV-1 strains from documented clinical context of resistance.
Investigation of in vitro viral escape will also be determined. Long-term
antiretroviral therapy often results in toxic adverse events attributable to
mitochondrial damage due to the inhibition of DNA polymerase ? synthesis
and the reduction of cellular energy production.

The toxicity of the new drugs will be evaluated by determining the inhibitory
properties (IC50) and insertion and exonucleolytic removal of new nucleoside
analogues by DNA polymerase ?. Finally, selected active compounds with
low in vitro cytotoxicity will be subjected to in vivo (in mice and/or rats)
pharmaco-toxicological investigations.

Background:

Human immunodeficiency virus (HIV) encodes for an RNA-dependent DNA
polymerase (reverse transcriptase, RT), but not the specific enzymes required
for the phosphorylation of 2’,3’-dideoxy- pyrymidine and purine nucleosides.
To exert antiviral activity, these analogues must undergo a three-step
phosphorylation by host cell kinases and/or be metabolized by other
enzymes. Their 5’-triphosphates act as RT competitive inhibitors and/or DNA
terminators. Since RT is essential to HIV replication, the development of RT
inhibitors is a key strategy in the fight against AIDS. But drug resistance
emerges rapidly with these nucleoside-based inhibitors (NRTIs).
At present, the emergence of HIV-1 variants resistant to standard drugs is one
of the major obstacles to chemotherapy of HIV-1 infection. HIV-1 can develop
multidrug resistance in patients receiving various combination chemotherapies.
Therefore the development of novel compounds especially modified 2’,3’-
dideoxynucleosides, which are active against wild-type as well as
multidrug-resistant variants, is urgently needed.

Aim:

The general aim of this project is to identify and prepare and identify new
potential drugs from the class of new modified 2’,3’-dideoxynucleosides,
active against HIV-1 drug-resistant laboratory and clinical strains.

Expected results:

To obtain new modified 2’, 3’-dideoxynucleosides and their phosphates;
highly active drugs against drug-resistant HIV strains, and to detect their
physico-chemical and biological properties. Results will be disseminated
through patenting.

Potential applications:

After obtaining positive biological results, patents and publications will be
submitted to a pharmaceutical firm (SME) for further investigations in animals
and in the clinic, allowing potential outlicensing of the above-mentioned drugs.